Thermodynamical Cross-Relations for Superconductors at the Critical Point

Grabiec, B.; Matlak, M.

doi:10.1002/1521-3951(200206)231:2<299::aid-pssb299>3.0.co;2-s

Cited by 8 publications

(8 citation statements)

References 23 publications

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“…This is due to the fact that the chemical potential enters the theoretical Kubo formula [31] for the electrical conductivity (resistivity). Thus, the critical behaviour of the chemical potential [23,24] should influence the temperature dependence of the contact electrode resistivity at critical points in the form of a fine substructure (kinks, minima, maxima) which can be registered. The proposed method can serve along with other conventional methods (specific heat, order parameter measurements, etc.)…”

Section: Introductionmentioning

confidence: 99%

Chemical potential induced phase transitions

Matlak

Molak

Pietruszka

2004

Physica Status Solidi (b)

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A simple electrical set-up to detect phase transitions is proposed and applied to a series of investigated samples: Gd, Cr, TiNi and CuZnSn, all exhibiting different types of phase transitions. The sample is glued to a contact electrode (here Ag) and immersed into a thermostat. We measure the electrical resistivity of the contact electrode as function of temperature. Due to the fact that the chemical potentials of the sample and the contact electrode should be equal (µ s = µ e ) the electron gas of the contact electrode "feels" a phase transition taking place in the investigated sample. Therefore we observe kinks in the resistivity plot of the contact electrode which easily localize the proper critical temperatures: T C (Gd), T N (Cr) and T struct (TiNi, CuZnSn). The proposed method visualizes the prevailing role of the chemical potential at phase transitions and provides a completely new ("remote") tool to detect critical points in solids. IntroductionThe chemical potential related to the electron gas of a system can be considered as a global quantity able to reflect all critical (or characteristic) points connected with different types of phase transitions (transformations) possible to appear in solids with varying temperature, pressure, concentration, etc. . Direct observation of the chemical potential critical behaviour has been performed by the use of electrochemical cells [21,22]. A quite new approach anticipated theoretically [25] is based on the temperature dependence of the resistivity of the contact electrode connected to a sample exhibiting phase transitions. Due to this method the critical temperatures of the sample should be observed as subtle but measurable kinks in the resisivity plot of the reference electrode. Astonishigly enough, the effect really exists. Here we report on some direct observations which allow to localize critical temperatures connected with different types of phase transitions taking place in Gd, Cr, TiNi and CuZnSn materials.

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Section: Introductionmentioning

confidence: 99%

Chemical potential induced phase transitions

Matlak

Molak

Pietruszka

2004

Physica Status Solidi (b)

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“…A very important result concerning the critical relations at the critical point, when taking into account the chemical potential of the system, has been given in Ref. [22] for superconductors and (generally) for the second order phase transitions in Ref. [23].…”

Section: Introductionmentioning

confidence: 99%

Phase transitions detection by means of a contact electrode

Matlak

Pietruszka

2003

Physica Status Solidi (b)

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We investigate theoretically and next experimentally a new possibility to detect critical temperatures of solids by means of a very simple electrical circuit consisting of an analyzed sample (exhibiting phase transitions) and a contact electrode (hereafter reference electrode) where the constant voltage is applied only to the latter one. The measured system is placed into a thermostat and the electric current flow through the reference electrode is measured as function of temperature. By assuming a model Hamiltonian for the probed sample describing ferromagnetic, superconducting or reentrant phase transitions and a one-band model for the contact electrode we calculate d.c. conductivity of the reference electrode. The temperature dependence of the conductivity of this electrode clearly indicates (in the form of kinks) the transition temperatures connected with phase transitions occurring in the investigated material. This is due to the fact that the chemical potential of the whole system in contact should equal at equilibrium. Our considerations suggest straightforward application of such a circuit in a direct laboratory praxis, especially because (beyond simplicity) the applied method possesses unlimited temperature range and can be considered as noninvasive with respect to the investigated sample. To verify the effect experimentally we have used as an investigated sample an antiferromagnetic Cr material and Cu as the reference electrode. The measurements of the resistivity R(Cr + Cu) and R(Cu) alone as functions of temperature made a possibility to plot the difference R(Cr + Cu) -R(Cu) vs temperature. This plot enabled to identify the critical Neel temperature of the Cr sample corresponding to the profound minimum in this curve.

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“…This behaviour has been demonstrated theoretically and experimentally in Refs. [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. For a given microscopic model, the chemical potential temperature dependence can be determined from the condition that the average number of the electrons in the investigated material is equal to a constant where the averaging procedure is performed within the grand canonical ensemble.…”

Section: Introductionmentioning

confidence: 69%

“…Thermodynamical critical relations including the chemical potential critical behaviour, valid at the critical point, have been demonstrated in Refs [4][5][6][7]12,13] results [6][7][8]10], obtained with the use of the work function method, confirmed experimentally the anomaly of the chemical potential at phase transitions. Another method to measure the chemical potential vs. temperature for metallic samples has been presented in Ref.…”

Section: Introductionmentioning

confidence: 99%